Examine source code of Print Extension

{
  "name": "Print Extension",
  "version": "3.2",
  "description": "Sends print job directly to the printers installed on the Chromebook",
  "permissions": [
    "printing"
  ],
  "browser_action": {
    "default_popup": "printers.html",
    "default_icon": "icons/icon.png"
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{2165368d-59c1-4172-a22f-ca108f1da3ab}"
    }
  }
}